U.S. Pat. No. 5,062,535 issued to Potter on Nov. 5, 1991, discloses a module library system having stationary and mobile racks. Each rack has vertical side panels that support a number of horizontal, cartridge-holding shelves. The stationary racks are arranged in two back-to-back rows, each having a plurality of racks arranged side-to-side. The open fronts of the stationary racks of one row face in a direction opposite to that of the other row.
The stationary racks in each row are connected side-to-side by spacers that fasten (e.g., using bolts) between upper and lower side walls of adjacent racks. Each rack is supported by a mounting base.
The mobile racks are arranged for side sliding motion in front of the rows of stationary racks so as not to block access to cartridges stored in the stationary racks. The mobile racks have rollers that ride on upper and lower tracks connected to the stationary racks.
In that patent, a break system is providing for stopping the movement of the mobile racks at selected locations along the tracks. The brake system includes padded members mounted to selected mobile racks, and stop members mounted to selected stationary racks, e.g., the stationary rack nearest the end of the row along which the mobile rack slides. As the mobile unit nears the end of its horizontal travel, the padded member frictionally engages the stop member, thereby abruptly stopping the mobile unit.
The system disclosed in that patent is generally suited to its intended purposes. Nevertheless there are certain areas in which improvements could be made. For instance, one problem encountered with that design in some applications is inadequacy of structural rigidity of the racks. This can be particularly acute where the racks are of significant height, e.g., near room height, and are of significant width. Such racks are particularly subject to a condition known as "racking," i.e., displacement of the sides of the racks out of plumb when the racks are loaded. Any solution to that problem, however, has to preserve the modularity of the library system, and permit easy assembly and disassembly of the racks.
Another area that could be improved is the braking system. The braking members disclosed in that patent can "jam" under certain circumstances when excessive engagement forces are applied, thus rendering it difficult to disengage or release the brakes. For example, this can happen when a user pushes one of the mobile racks too hard, causing it to move at a high speed, thereby causing the brake members to "over" engage with one another.
Yet another area deserving of attention is the track arrangements on which the mobile racks ride. It would be desirable to improve the mechanical strength and structural rigidity of the upper and lower track arrangements, and to provide an improved track design that prevents or at least reduces derailment, e.g., during braking.
Accordingly, it would be desirable to provide a new and improved library system that overcomes a number of these and other drawbacks with the known design.